This proposal addresses Research Objective 21, Data Collection In Population Aging. The principal investigator is an established statistical Investigator with broad background In the development and application of statistical models to demographic, health, and social science data. The proposal outlines the start of a methodological research program to enhance the study of chronic disability over time. It focuses on disability data arising from the National Long Term Care Survey and statistical methods currently used for their analysis. The long term goal of the PI and his collaborators is to develop new statistical methodology for the analysis of survey-based longitudinal disability data and new statistical tools to preserve the confidentiality of the data sources while making them more broadly available for analysis by others. The principal investigator is a "New Investigator" under NIH definition because he has not worked in this area before. Nonetheless, he is an established researcher with considerable experience in relevant aspects of statistical modeling and disclosure limitation methodology.